If you want to rotate the turret and shoot with the mouse, you must right-click with your mouse to enable this mode. Right-click again to disable the mode and make the cursor visible again. Note that you will not be able to rotate the turret or shoot with the mouse if you have not simulated theses touches:

"Shooting game: drag the button to sight": Drag this to somewhere to the right of the sight.

"Shooting game: drag the button to fire": Drag this to the shoot button.